Is it legal to say that MyGame supports other (specific) games' textures, sounds and models?

I'd like to get involved into an open source game project and implement support for Quake's weapon models (for example), but the owners of the project don't know about the legal aspect of it, so I'm asking here.

4 Answers
4

It depends on the third party. Valve's SDK, for example, prohibits use of it for anything other than mods running on the Half Life engines, so if you were to use their formats you would be in violation. Other third parties may have different or similar terms.

All of the Quake data files remain copyrighted and licensed under the
original terms, so you cannot redistribute data from the original game, but if
you do a true total conversion, you can create a standalone game based on
this code.

--- snip ---

You can still download one of
the original quake demos and use that data with the code, but there are
restrictions on the redistribution of the demo data.

If you never actually bought a complete version of Quake, you might want
to rummage around in a local software bargain bin for one of the originals,
or perhaps find a copy of the "Quake: the offering" boxed set with both
mission packs.

The only company that can truly answer your question would be ID software, if they consider your game to be in violation of their copyrights then they will most likely take legal action regardless of what anyone here tells you. On the other hand, they have released the source code of Quake in a manner that allows you to modify it as long as you don't distribute the other files with your modifications.

You may wish to consider that by making the game "borrow" models from another game installed on the users computer you will never be able to make a full installation that does not require that game. In short, you will artificially shrink your potential user base, all to save yourself the relatively short time it would take to make a suitable weapon (and projectile) model in a 3D program.

Personally I would use Blender and make a quick weapon myself, even if it looks crude it would be safe to use and could be upgraded in the future without any legal dilemmas.

Quake assets are an example of what I'm trying to do. The idea is to be able to openly claim support of third party content (as well as actually have working support) and not be sued over it. Most companies allow personal use of their products' assets in case you have purchased them, so I'm not going to distribute any content users may not own, they will have to get it themselves one way or another for it to work.
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user1306322Aug 2 '12 at 12:52

Irrlicht 3d engine openly claims support for various Quake formats, among others

Blender openly claims support for a multitude of model formats, including Quake's md2

Assimp asset loading library openly claims support for Quake's models as well as others

You should be safe if you claim support for other product's asset formats. Directly claiming support for other game's data might be ok too, but the user could be in violation depending on the EULA and such - you yourself commented that many allow personal use, so check it for each one in your mind. Examples of open-source games that depend on the original data are Arx Libertatis and OpenMW.

Regarding implementation, I think the main issue is whether the file formats contain patented features in which case it would be illegal to implement in some countries. This is most frequently encountered in formats that attempt some kind of compression, such as audio/video files.